1. Field of Invention
The present invention relates to a copper-based metallic member haaving a chemical conversion phosphate film, particularly an insulated copper-electric wire, and to a method for forming a chemical conversion phosphate film, such as a zinc phosphate film, on a copper-based metallic member. More particularly, the present invention relates to a copper-based metallic member having an improved rust-proofing characteristic, and an improved lubrication characteristic at press forming. In addition, the present invention relates to an electric copper wire with insulation which is used for wires including a coil-winding for converting electric power to magnetic energy, wire for an electric power transmission, cabtyre cable and cords, and relates to a method for forming a chemical conversion film having an electric-insulation characteristic and a lubrication characteristic.
2. Description of the Related Art
It is known to subject iron-based material to a chemical conversion treatment to form a zinc phosphate film or a zinc chromic acid film on the surface of the material. Iron-based material undergoing the chemical conversion treatment has excellent characteristics enabling it to be used in various fields. On the other hand, since copper is chemically stable, it was heretofore difficult to apply the chemical conversion treatment, such as used for the iron-based material, to copper-based metallic members. The known chemical conversion treatments for copper-based metallic members are different from those for iron-based material. In one such treatment, a copper-based metallic member is treated in an aqueous solution containing potassium chlorate or potassium per chlorate at a temperature of from 80.degree. C. to 90.degree. C. for a period of 5 to 10 minutes, thereby obtaining a copper-based metallic member having a cuprous oxide film. In another such treatment, a copper-based metallic member is treated in an aqueous solution containing sodium hydroxide and potassium persulfate, thereby obtaining a copper-based metallic member having a cupric oxide film. The former method is referred to as the cuprous-oxide method, and the latter method is referred to as the black copper-oxide method.
It is also known to treat copper-based metallic member with chromic acid.
The copper-based metallic member having the copper oxide film is less reactive than the chemically converted iron-based material, and therefore, any coating thereon does not exhibit excellent properties. Furthermore, the procedures for the known chemical conversion treatments for a copper-based metallic member are complicated. Accordingly, the known chemical conversion treatments for copper have been limited in use.
In this connection, a phosphate film has a high reactivity and is preferable. Where a phosphate film is necessary as, for example, an undercoat for another coating, zinc is galvanized on the copper-based metallic member, and is then treated by the phosphating process. This causes problems in the operating efficiency, cost, and the like.
Heretofore, copper electric wires with insulation were produced by applying insulating coating on the copper electric-wire base and baking the insulating coating (a synthetic enamel wire); winding an insulating fiber around the copper electric-wire base (a fiber-wound wire); or, combining these methods to form a composite insulation. These copper electric wires are widely used in generators, motors, transformers, and the like.
Along with a recent tendency toward enhancing the capacity and voltage and minutuarizing of electric machinery and devices, electric devices and the like in automobiles are required to withstand strict environmental and operating conditions. The conventional copper electric-wires used in such electric devices are therefore required to have excellent insulation characteristics. In order to meet such a requirement, the chemical conversion film cannot be utilized because such a film having a good reactivity cannot be directly and firmly formed on the copper surface, instead, one or two layers of organic insulating material, which are directly deposited or coated on the copper electric-wire, are utilized. The layer(s) of organic insulating material have therefore the disadvantage in that they are easily damaged during the coiling necessary in the production of an electric wire, so that current leakage through the damaged layer(s) occurs. In the case of a synthesized enamel wire, when the film has been stretched or bent and then comes into contact with water or a solvent, an abnormality referred to as "crazing" occurs in which apparently minute cracks are formed in the film.